Stabilization of synthetic polymers

ABSTRACT

Synthetic polymers which possess outstanding stability to oxidative, thermal or light-induced degradation comprise as stabilizer at least a compound of the formula I 
                 
 
wherein
         R 1  and R 2  are each independently of one another hydrogen or C 1 -C 8 alkyl,   R 3  and R 4  are each independently of one another C 1 -C 12 alkyl, and   R 5  is C 1 -C 7 alkyl.

The present invention relates to compositions comprising a synthetic polymer subject to oxidative, thermal or light-induced degradation, especially polyolefins, polyether polyol or polyurethane, and as stabilizer a specific group of compounds of the benzofuran-2-one type.

The use of compounds of the benzofuran-2-one type as stabilizers for synthetic polymers is known, for example, from WO-A-80/01566 or U.S. Pat. No. 5,516,920.

The known stabilizers do not satisfy in every respect the high requirements which a stabilizer is required to meet, especially with regard to shelf life, water absorption, sensitivity to hydrolysis, in-process stabilization, color properties, volatility, migration behaviour, compatibility and improvement in protection against light. As a result there continues to be a need for effective stabilizers for synthetic polymers that are sensitive to oxidative, thermal and/or light-induced degradation.

EP-A-0 871 066 discloses the use of a specific group of compounds of the benzofuran-2-one type as DOX scavengers in color photographic materials.

It has now been found that a specific group of compounds of the benzofuran-2-one type disclosed in EP-A-0 871 066 is particularly suitable as a stabilizer for synthetic polymers which are sensitive to oxidative, thermal or light-induced degradation.

The present invention therefore provides compositions comprising

-   -   a) a synthetic polymer subject to oxidative, thermal or         light-induced degradation, and     -   b) at least a compound of the formula I     -    wherein         -   R₁ and R₂ are each independently of one another hydrogen or             C₁-C₈alkyl,         -   R₃ and R₄ are each independently of one another C₁-C₁₂alkyl,             and         -   R₅ is C₁-C₇alkyl.

Alkyl having up to 12 carbon atoms is a branched or unbranched radical, for example methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1,1,3,3-tetra-methylbutyl (tert-octyl), 1-methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl or dodecyl. One of the preferred definitions for R₁ and R₂ is, for example, C₁-C₆alkyl, especially C₁-C₄alkyl, e.g. tert-butyl. Preferably, R₃ and R₄ are C₄-C₁₂alkyl, especially C₄-C₁₀alkyl, e.g. C₈alkyl. A preferred definition of R₅ is C₁-C₄alkyl, especially C₁-C₃alkyl, e.g. methyl.

Preferred compounds of the formula I are those wherein

-   R₁ and R₂ are each independently of one another hydrogen or     C₁-C₄alkyl, -   R₃ and R₄ are each independently of one another C₄-C₁₀alkyl, and -   R₅ is C₁-C₄alkyl.

Further preferred compounds of the formula I are those wherein R₃ and R₄ are tert-octyl.

Of special interest is the compound of the formula I wherein

-   R₁ and R₂ are hydrogen, -   R₃ and R₄ are tert-octyl, and -   R₅ is methyl.

The synthesis of the compounds of the formula I is for example disclosed in EP-A-0 871 066.

The compounds of the formula I are suitable for stabilizing synthetic polymers against oxidative, thermal or light-induced degradation.

Examples of such materials are:

-   1. Polymers of monoolefins and diolefins, for example polypropylene,     polyisobutylene, polybut-1-ene, poly-4-methylpent-1-ene,     polyvinylcyclohexane, polyisoprene or polybutadiene, as well as     polymers of cycloolefins, for instance of cyclopentene or     norbornene, polyethylene (which optionally can be crosslinked), for     example high density polyethylene (HDPE), high density and high     molecular weight polyethylene (HDPE-HMW), high density and ultrahigh     molecular weight polyethylene (HDPE-UHMW), medium density     polyethylene (MDPE), low density polyethylene (LDPE), linear low     density polyethylene (LLDPE), (VLDPE) and (ULDPE).

Polyolefins, i.e. the polymers of monoolefins exemplified in the preceding paragraph, preferably polyethylene and polypropylene, can be prepared by different, and especially by the following, methods:

-   -   a) radical polymerisation (normally under high pressure and at         elevated temperature).     -   b) catalytic polymerisation using a catalyst that normally         contains one or more than one metal of groups IVb, Vb, VIb or         VIII of the Periodic Table. These metals usually have one or         more than one ligand, typically oxides, halides, alcoholates,         esters, ethers, amines, alkyls, alkenyls and/or aryls that may         be either π- or σ-coordinated. These metal complexes may be in         the free form or fixed on substrates, typically on activated         magnesium chloride, titanium(III) chloride, alumina or silicon         oxide. These catalysts may be soluble or insoluble in the         polymerisation medium. The catalysts can be used by themselves         in the polymerisation or further activators may be used,         typically metal alkyls, metal hydrides, metal alkyl halides,         metal alkyl oxides or metal alkyloxanes, said metals being         elements of groups Ia, IIa and/or IIIa of the Periodic Table.         The activators may be modified conveniently with further ester,         ether, amine or silyl ether groups. These catalyst systems are         usually termed Phillips, Standard Oil Indiana, Ziegler (-Natta),         TNZ (DuPont), metallocene or single site catalysts (SSC).

-   2. Mixtures of the polymers mentioned under 1), for example mixtures     of polypropylene with polyisobutylene, polypropylene with     polyethylene (for example PP/HDPE, PP/LDPE) and mixtures of     different types of polyethylene (for example LDPE/HDPE).

-   3. Copolymers of monoolefins and diolefins with each other or with     other vinyl monomers, for example ethylene/propylene copolymers,     linear low density polyethylene (LLDPE) and mixtures thereof with     low density polyethylene (LDPE), propylene/but-1-ene copolymers,     propylene/isobutylene copolymers, ethylene/but-1-ene copolymers,     ethylene/hexene copolymers, ethylene/methylpentene copolymers,     ethylene/heptene copolymers, ethylene/octene copolymers,     ethylene/vinylcyclohexane copolymers, ethylene/cycloolefin     copolymers (e.g. ethylene/norbornene like COC), ethylene/1-olefins     copolymers, where the 1-olefin is generated in-situ;     propylene/butadiene copolymers, isobutylene/isoprene copolymers,     ethylene/vinylcyclohexene copolymers, ethylene/alkyl acrylate     copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl     acetate copolymers or ethylene/acrylic acid copolymers and their     salts (ionomers) as well as terpolymers of ethylene with propylene     and a diene such as hexadiene, dicyclopentadiene or     ethylidene-norbornene; and mixtures of such copolymers with one     another and with polymers mentioned in 1) above, for example     polypropylene/ethylene-propylene copolymers, LDPE/ethylene-vinyl     acetate copolymers (EVA), LDPE/ethylene-acrylic acid copolymers     (EAA), LLDPE/EVA, LLDPE/EAA and alternating or random     polyalkylene/carbon monoxide copolymers and mixtures thereof with     other polymers, for example polyamides.

-   4. Hydrocarbon resins (for example C₅-C₉) including hydrogenated     modifications thereof (e.g. tackifiers) and mixtures of     polyalkylenes and starch.

Homopolymers and copolymers from 1.)-4.) may have any stereostructure including syndiotactic, isotactic, hemi-isotactic or atactic; where atactic polymers are preferred. Stereoblock polymers are also included.

-   5. Polystyrene, poly(p-methylstyrene), poly(α-methylstyrene). -   6. Aromatic homopolymers and copolymers derived from vinyl aromatic     monomers including styrene, α-methylstyrene, all isomers of vinyl     toluene, especially p-vinyltoluene, all isomers of ethyl styrene,     propyl styrene, vinyl biphenyl, vinyl naphthalene, and vinyl     anthracene, and mixtures thereof. Homopolymers and copolymers may     have any stereostructure including syndiotactic, isotactic,     hemi-isotactic or atactic; where atactic polymers are preferred.     Stereoblock polymers are also included. -   6a. Copolymers including aforementioned vinyl aromatic monomers and     comonomers selected from ethylene, propylene, dienes, nitriles,     acids, maleic anhydrides, maleimides, vinyl acetate and vinyl     chloride or acrylic derivatives and mixtures thereof, for example     styrene/butadiene, styrene/acrylonitrile, styrene/ethylene     (interpolymers), styrene/alkyl methacrylate, styrene/butadiene/alkyl     acrylate, styrene/butadiene/alkyl methacrylate, styrene/maleic     anhydride, styrene/acrylonitrile/methyl acrylate; mixtures of high     impact strength of styrene copolymers and another polymer, for     example a polyacrylate, a diene polymer or an     ethylene/propylene/diene terpolymer; and block copolymers of styrene     such as styrene/butadiene/styrene, styrene/isoprene/styrene,     styrene/ethylene/butylene/styrene or     styrene/ethylene/propylene/styrene. -   6b. Hydrogenated aromatic polymers derived from hydrogenation of     polymers mentioned under 6.), especially including     polycyclohexylethylene (PCHE) prepared by hydrogenating atactic     polystyrene, often referred to as polyvinylcyclohexane (PVCH). -   6c. Hydrogenated aromatic polymers derived from hydrogenation of     polymers mentioned under 6a.).

Homopolymers and copolymers may have any stereostructure including syndiotactic, isotactic, hemi-isotactic or atactic; where atactic polymers are preferred. Stereoblock polymers are also included.

-   7. Graft copolymers of vinyl aromatic monomers such as styrene or     α-methylstyrene, for example styrene on polybutadiene, styrene on     polybutadiene-styrene or polybutadiene-acrylonitrile copolymers;     styrene and acrylonitrile (or methacrylonitrile) on polybutadiene;     styrene, acrylonitrile and methyl methacrylate on polybutadiene;     styrene and maleic anhydride on polybutadiene; styrene,     acrylonitrile and maleic anhydride or maleimide on polybutadiene;     styrene and maleimide on polybutadiene; styrene and alkyl acrylates     or methacrylates on polybutadiene; styrene and acrylonitrile on     ethylene/propylene/diene terpolymers; styrene and acrylonitrile on     polyalkyl acrylates or polyalkyl methacrylates, styrene and     acrylonitrile on acrylate/butadiene copolymers, as well as mixtures     thereof with the copolymers listed under 6), for example the     copolymer mixtures known as ABS, MBS, ASA or AES polymers. -   8. Halogen-containing polymers such as polychloroprene, chlorinated     rubbers, chlorinated and brominated copolymer of     isobutylene-isoprene (halobutyl rubber), chlorinated or     sulfo-chlorinated polyethylene, copolymers of ethylene and     chlorinated ethylene, epichlorohydrin homo- and copolymers,     especially polymers of halogen-containing vinyl compounds, for     example polyvinyl chloride, polyvinylidene chloride, polyvinyl     fluoride, polyvinylidene fluoride, as well as copolymers thereof     such as vinyl chloride/vinylidene chloride, vinyl chloride/vinyl     acetate or vinylidene chloride/vinyl acetate copolymers. -   9. Polymers derived from α,β-unsaturated acids and derivatives     thereof such as polyacrylates and polymethacrylates; polymethyl     methacrylates, polyacrylamides and polyacrylonitriles,     impact-modified with butyl acrylate. -   10. Copolymers of the monomers mentioned under 9) with each other or     with other unsaturated monomers, for example acrylonitrile/butadiene     copolymers, acrylonitrile/alkyl acrylate copolymers,     acrylonitrile/alkoxyalkyl acrylate or acrylonitrile/vinyl halide     copolymers or acrylonitrile/alkyl methacrylate/butadiene     terpolymers. -   11. Polymers derived from unsaturated alcohols and amines or the     acyl derivatives or acetals thereof, for example polyvinyl alcohol,     polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl     maleate, polyvinyl butyral, polyallyl phthalate or polyallyl     melamine; as well as their copolymers with olefins mentioned in 1)     above. -   12. Homopolymers and copolymers of cyclic ethers such as     polyalkylene glycols, polyethylene oxide, polypropylene oxide or     copolymers thereof with bisglycidyl ethers. -   13. Polyacetals such as polyoxymethylene and those polyoxymethylenes     which contain ethylene oxide as a comonomer; polyacetals modified     with thermoplastic polyurethanes, acrylates or MBS. -   14. Polyphenylene oxides and sulfides, and mixtures of polyphenylene     oxides with styrene polymers or polyamides. -   15. Polyurethanes derived from hydroxyl-terminated polyethers,     polyesters or polybutadienes on the one hand and aliphatic or     aromatic polyisocyanates on the other, as well as precursors     thereof. -   16. Polyamides and copolyamides derived from diamines and     dicarboxylic acids and/or from aminocarboxylic acids or the     corresponding lactams, for example polyamide 4, polyamide 6,     polyamide 6/6, 6/10, 6/9, 6/12, 4/6, 12/12, polyamide 11, polyamide     12, aromatic polyamides starting from m-xylene diamine and adipic     acid; polyamides prepared from hexamethylenediamine and isophthalic     or/and terephthalic acid and with or without an elastomer as     modifier, for example poly-2,4,4,-trimethylhexamethylene     terephthalamide or poly-m-phenylene isophthalamide; and also block     copolymers of the aforementioned polyamides with polyolefins, olefin     copolymers, ionomers or chemically bonded or grafted elastomers; or     with polyethers, e.g. with polyethylene glycol, polypropylene glycol     or polytetramethylene glycol; as well as polyamides or copolyamides     modified with EPDM or ABS; and polyamides condensed during     processing (RIM polyamide systems). -   17. Polyureas, polyimides, polyamide-imides, polyetherimids,     polyesterimids, polyhydantoins and polybenzimidazoles. -   18. Polyesters derived from dicarboxylic acids and diols and/or from     hydroxycarboxylic acids or the corresponding lactones, for example     polyethylene terephthalate, polybutylene terephthalate,     poly-1,4-dimethylolcyclohexane terephthalate, polyalkylene     naphthalate (PAN) and polyhydroxybenzoates, as well as block     copolyether esters derived from hydroxyl-terminated polyethers; and     also polyesters modified with polycarbonates or MBS. -   19. Polycarbonates and polyester carbonates. -   20. Polyketones. -   21. Polysulfones, polyether sulfones and polyether ketones. -   22. Crosslinked polymers derived from aldehydes on the one hand and     phenols, ureas and melamines on the other hand, such as     phenol/formaldehyde resins, urea/formaldehyde resins and     melamine/formaldehyde resins. -   23. Drying and non-drying alkyd resins. -   24. Unsaturated polyester resins derived from copolyesters of     saturated and unsaturated dicarboxylic acids with polyhydric     alcohols and vinyl compounds as crosslinking agents, and also     halogen-containing modifications thereof of low flammability. -   25. Crosslinkable acrylic resins derived from substituted acrylates,     for example epoxy acrylates, urethane acrylates or polyester     acrylates. -   26. Alkyd resins, polyester resins and acrylate resins crosslinked     with melamine resins, urea resins, isocyanates, isocyanurates,     polyisocyanates or epoxy resins. -   27. Crosslinked epoxy resins derived from aliphatic, cycloaliphatic,     heterocyclic or aromatic glycidyl compounds, e.g. products of     diglycidyl ethers of bisphenol A and bisphenol F, which are     crosslinked with customary hardeners such as anhydrides or amines,     with or without accelerators. -   28. Blends of the aforementioned polymers (polyblends), for example     PP/EPDM, Polyamide/EPDM or ABS, PVC/EVA, PVC/ABS, PVC/MBS, PC/ABS,     PBTP/ABS, PC/ASA, PC/PBT, PVC/CPE, PVC/acrylates, POM/thermoplastic     PUR, PC/thermoplastic PUR, POM/acrylate, POM/MBS, PPO/HIPS, PPO/PA     6.6 and copolymers, PA/HDPE, PA/PP, PA/PPO, PBT/PC/ABS or     PBT/PET/PC.

The synthetic polymers to be protected are preferably thermoplastic polymers, especially polyolefins, polyether polyols or polyurethanes, in particular polyethylene and polypropylene or copolymers thereof with mono- and diolefins.

The compounds of the formula I are likewise used for polyurethane production, especially for preparing flexible polyurethane foams. In this context the novel compositions and the products produced therefrom are effectively protected against degradation. In particular, scorching during foam production is avoided. Polyurethane foamers may post-add phospites as plasticizers such as diphenyl isodecyl phosphite (DPDP), phenyl diisodecyl phosphite (PDDP) to the base stabilized polyether polyols at the mixing head prior to the foaming in relative high concentrations (up to 1.5% by weight based on the polyether polyol). In the presence of this high amount of phosphites the formed polyurethane foams show an undesired discoloration (pinking and/or yellowing). However, in the presence of the compounds of the formula I the polyurethane foams are white.

The polyurethanes are obtained, for example, by reacting polyethers, polyesters and polybutadienes which contain terminal hydroxyl groups with aliphatic or aromatic polyisocyanates.

Polyethers having terminal hydroxyl groups are known and are prepared, for example, by polymerizing epoxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with themselves, for example in the presence of BF₃, or by addition reaction of these epoxides, alone or as a mixture or in succession, with starting components containing reactive hydrogen atoms, such as water, alcohols, ammonia or amines, for example ethylene glycol, propylene 1,3- and 1,2-glycol, trimethylolpropane, 4,4′-dihydroxydiphenylpropane, aniline, ethanolamine or ethylenediamine. Sucrose polyethers are also suitable in accordance with the invention. In many cases preference is given to those polyethers which predominantly (up to 90% by weight, based on all the OH groups present in the polyether) contain primary OH groups. Furthermore, polyethers modified by vinyl polymers, as are formed, for example, by polymerizing styrene and acrylonitrile in the presence of polyethers, are suitable, as are polybutadienes containing OH groups.

These compounds generally have molecular weights of 40 and are polyhydroxy compounds, especially compounds containing from two to eight hydroxyl groups, especially those of molecular weight from 800 to 10 000, preferably from 1000 to 6000, for example polyethers containing at least 2, generally 2 to 8, but preferably 2 to 4, hydroxyl groups, as are known for the preparation of homogeneous polyurethanes and cellular polyurethanes.

It is of course possible to employ mixtures of the above compounds containing at least two isocyanate-reactive hydrogen atoms, in particular with a molecular weight of 400-10 000.

Suitable polyisocyanates are aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, for example ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane 1,3- and -1,4-diisocyanate and also any desired mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 2,4- and 2,6-hexahydrotolylene diisocyanate and also any desired mixtures of these isomers, hexahydro-1,3- and/or -1,4-phenylene diisocyanate, perhydro-2,4′- and/or -4,4′-diphenylmethanediisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate, and also any desired mixtures of these isomers, diphenylmethane 2,4′- and/or -4,4′-diisocyanate, naphthylene 1,5-diisocyanate, triphenylmethane 4,4′,4″-triisocyanate, polyphenyl-polymethylene polyisocyanates as are obtained by aniline-formaldehyde condensation followed by phosgenization, m- and p-isocyanatophenylsulfonyl isocyanates, perchlorinated aryl polyisocyanates, polyisocyanates containing carbodiimide groups, polyisocyanates containing allophanate groups, polyisocyanates containing isocyanurate groups, polyisocyanates containing urethane groups, polyisocyanates containing acylated urea groups, polyisocyanates containing biuret groups, polyisocyanates containing ester groups, reaction products of the abovementioned isocyanates with acetals, and polyisocyanates containing polymeric fatty acid radicals.

It is also possible to employ the isocyanate group-containing distillation residues, as they are or dissolved in one or more of the abovementioned polyisocyanates, which are obtained in the course of the industrial preparation of isocyanates. It is additionally possible to use any desired mixtures of the abovementioned polyisocyanates.

Particular preference is given in general to the polyisocyanates which are readily obtainable industrially, for example 2,4- and 2,6-tolylene diisocyanate and any desired mixtures of these isomers (“TDI”), polyphenyl-polymethylene-polyisocyanates as prepared by aniline-formaldehyde condensation followed by phosgenization (“crude MDI”), and polyisocyanates containing carbodiimide, urethane, allophanate, isocyanurate, urea or biuret groups (“modified polyisocyanates”).

Particular emphasis is to be placed on the action of the compounds of the formula I against thermal and oxidative degradation, especially under thermal stress as occurs during the processing of thermoplastics. The compounds of the formula I are therefore outstandingly suitable for use as in-process stabilizers.

The compounds of the formula I are preferably added to the synthetic polymer to be stabilized in an amount of from 0.0005 to 10%, in particular from 0.001 to 2%, for example from 0.01 to 2%, based on the weight of the synthetic polymer to be stabilized.

In addition to components (a) and (b) the novel compositions may comprise further costabilizers (additives) such as, for example, the following:

1. Antioxidants

-   1.1. Alkylated monophenols, for example     2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-dimethylphenol,     2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol,     2,6-di-tert-butyl-4-isobutylphenol,     2,6-dicyclopentyl-4-methylphenol,     2-(α-methylcyclohexyl)-4,6-dimethylphenol,     2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol,     2,6-di-tert-butyl-4-methoxymethylphenol, nonylphenols which are     linear or branched in the side chains, for example     2,6-di-nonyl-4-methylphenol,     2,4-dimethyl-6-(1′-methylundec-1′-yl)phenol,     2,4-dimethyl-6-(1′-methylheptadec-1′-yl)phenol,     2,4-dimethyl-6-(1′-methyltridec-1′-yl)phenol and mixtures thereof. -   1.2. Alkylthiomethylphenols, for example     2,4-dioctylthiomethyl-6-tert-butylphenol,     2,4-dioctylthiomethyl-6-methylphenol,     2,4-dioctylthiomethyl-6-ethylphenol,     2,6-di-dodecylthiomethyl-4-nonylphenol. -   1.3. Hydroquinones and alkylated hydroquinones, for example     2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butylhydroquinone,     2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4-octadecyloxyphenol,     2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole,     3,5-di-tert-butyl-4-hydroxyanisole,     3,5-di-tert-butyl-4-hydroxyphenyl stearate,     bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate. -   1.4. Tocopherols, for example α-tocopherol, β-tocopherol,     γ-tocopherol, δ-tocopherol and mixtures thereof (vitamin E). -   1.5. Hydroxylated thiodiphenyl ethers, for example     2,2′-thiobis(6-tert-butyl-4-methylphenol),     2,2′-thiobis(4-octylphenol),     4,4′-thiobis(6-tert-butyl-3-methylphenol),     4,4′-thiobis(6-tert-butyl-2-methylphenol),     4,4′-thiobis(3,6-di-sec-amylphenol),     4,4′-bis(2,6-dimethyl-4-hydroxyphenyl)disulfide. -   1.6. Alkylidenebisphenols, for example     2,2′-methylenebis(6-tert-butyl-4-methylphenol),     2,2′-methylenebis(6-tert-butyl-4-ethylphenol),     2,2′-methylenebis[4-methyl-6-(α-methylcyclohexyl)phenol],     2,2′-methylenebis(4-methyl-6-cyclohexylphenol),     2,2′-methylenebis(6-nonyl-4-methylphenol),     2,2′-methylenebis(4,6-di-tert-butylphenol),     2,2′-ethylidenebis(4,6-di-tert-butylphenol),     2,2′-ethylidenebis(6-tert-butyl-4-isobutylphenol),     2,2′-methylenebis[6-(α-methylbenzyl)-4-nonylphenol],     2,2′-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol],     4,4′-methylenebis(2,6-di-tert-butylphenol),     4,4′-methylenebis(6-tert-butyl-2-methylphenol),     1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,     2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,     1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,     1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane,     ethylene glycol     bis[3,3-bis(3′-tert-butyl-4′-hydroxyphenyl)butyrate],     bis(3-tert-butyl-4-hydroxy-5-methyl-phenyl)dicyclopentadiene,     bis[2-(3′-tert-butyl-2′-hydroxy-5′-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate,     1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butane,     2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane,     2,2-bis-(5-tert-butyl-4-hydroxy2-methylphenyl)-4-n-dodecylmercaptobutane,     1,1,5,5-tetra(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane. -   1.7. O-, N- and S-benzyl compounds, for example     3,5,3′,5′-tetra-tert-butyl-4,4′-dihydroxydibenzyl ether,     octadecyl-4-hydroxy-3,5-dimethylbenzylmercaptoacetate,     tridecyl-4-hydroxy-3,5-di-tert-butylbenzylmercaptoacetate,     tris(3,5-di-tert-butyl-4-hydroxybenzyl)amine,     bis(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)dithioterephthalate,     bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide,     isooctyl-3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate. -   1.8. Hydroxybenzylated malonates, for example     dioctadecyl-2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)malonate,     di-octadecyl-2-(3-tert-butyl-4-hydroxy-5-methylbenzyl)malonate,     didodecylmercaptoethyl-2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate,     bis[4-(1,1,3,3-tetramethylbutyl)phenyl]-2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate. -   1.9. Aromatic hydroxybenzyl compounds, for example     1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene,     1,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzene,     2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol. -   1.10. Triazine compounds, for example     2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazine,     2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazine,     2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,3,5-triazine,     2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,2,3-triazine,     1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,     1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate,     2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine,     1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-hexahydro-1,3,5-triazine,     1,3,5-tris(3,5-dicyclohexyl-4-hydroxybenzyl)isocyanurate. -   1.11. Benzylphosphonates, for example     dimethyl-2,5-di-tert-butyl-4-hydroxybenzylphosphonate,     diethyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate,     dioctadecyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate,     dioctadecyl-5-tert-butyl-4-hydroxy-3-methylbenzylphosphonate, the     calcium salt of the monoethyl ester of     3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid. -   1.12. Acylaminophenols, for example 4-hydroxylauranilide,     4-hydroxystearanilide, octyl     N-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate. -   1.13. Esters of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid     with mono- or polyhydric alcohols, e.g. with methanol, ethanol,     n-octanol, i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol,     ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene     glycol, diethylene glycol, triethylene glycol, pentaerythritol,     tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,     3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,     trimethylolpropane,     4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane. -   1.14. Esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic     acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol,     n-octanol, i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol,     ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene     glycol, diethylene glycol, triethylene glycol, pentaerythritol,     tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,     3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,     trimethylolpropane,     4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane;     3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]-undecane. -   1.15. Esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid     with mono- or polyhydric alcohols, e.g. with methanol, ethanol,     octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene     glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol,     diethylene glycol, triethylene glycol, pentaerythritol,     tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,     3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,     trimethylolpropane,     4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane. -   1.16. Esters of 3,5-di-tert-butyl-4-hydroxyphenyl acetic acid with     mono- or polyhydric alcohols, e.g. with methanol, ethanol, octanol,     octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,     1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene     glycol, triethylene glycol, pentaerythritol,     tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,     3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,     trimethylolpropane,     4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane. -   1.17. Amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid     e.g.     N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexamethylenediamide,     N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)trimethylenediamide,     N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazide,     N,N′-bis[2-(3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyloxy)ethyl]oxamide     (Naugard®XL-1, supplied by Uniroyal). -   1.18. Ascorbic acid (vitamin C) -   1.19. Aminic antioxidants, for example     N,N′-di-isopropyl-p-phenylenediamine,     N,N′-di-sec-butyl-p-phenylenediamine,     N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine,     N,N′-bis(1-ethyl-3methylpentyl)-p-phenylenediamine,     N,N′-bis(1-methylheptyl)-p-phenylenediamine,     N,N′-dicyclohexyl-p-phenylenediamine,     N,N′-diphenyl-p-phenylenediamine,     N,N′-bis(2-naphthyl)-p-phenylenediamine,     N-isopropyl-N′-phenyl-p-phenylenediamine,     N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine,     N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine,     N-cyclohexyl-N′-phenyl-p-phenylenediamine,     4-(p-toluenesulfamoyl)diphenylamine,     N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine,     N-allyldiphenylamine, 4-isopropoxydiphenylamine,     N-phenyl-1-naphthylamine, N-(4-tert-octylphenyl)-1-naphthylamine,     N-phenyl-2-naphthylamine, octylated diphenylamine, for example     p,p′-di-tert-octyldiphenylamine, 4-n-butyl-aminophenol,     4-butyrylaminophenol, 4-nonanoylaminophenol,     4-dodecanoylaminophenol, 4-octadecanoylaminophenol,     bis(4-methoxyphenyl)amine,     2,6-di-tert-butyl-4-dimethylaminomethylphenol,     2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,     N,N,N′,N′-tetra-methyl-4,4′-diaminodiphenylmethane,     1,2-bis[(2-methylphenyl)amino]ethane, 1,2-bis(phenylamino)propane,     (o-tolyl)biguanide, bis[4-(1′,3′-dimethylbutyl)phenyl]amine,     tert-octylated N-phenyl-1-naphthylamine, a mixture of mono- and     dialkylated tert-butyl/tert-octyldiphenylamines, a mixture of mono-     and dialkylated nonyldiphenylamines, a mixture of mono- and     dialkylated dodecyldiphenylamines, a mixture of mono- and     dialkylated isopropyl/isohexyldiphenylamines, a mixture of mono- and     dialkylated tert-butyldiphenylamines,     2,3-dihydro-3,3-dimethyl-4H-1,4-benzothiazine, phenothiazine, a     mixture of mono- and dialkylated     tert-butyl/tert-octylphenothiazines, a mixture of mono- and     dialkylated tert-octylphenothiazines, N-allylphenothiazine,     N,N,N′,N′-tetraphenyl-1,4-diaminobut-2-ene.     2. UV Absorbers and Light Stabilizers -   2.1. 2-(2′-Hydroxyphenyl)benzotriazoles, for example     2-(2′-hydroxy-5′-methylphenyl)benzotriazole,     2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)benzotriazole,     2-(5′-tert-butyl-2′-hydroxyphenyl)benzotriazole,     2-(2′-hydroxy-5′-(1,1,3,3-tetramethylbutyl)phenyl)benzotriazole,     2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)-5-chlorobenzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-methylphenyl)-5-chlorobenzotriazole,     2-(3′-sec-butyl-5′-tert-butyl-2′-hydroxyphenyl)benzotriazole,     2-(2′-hydroxy-4′-octyloxyphenyl)benzotriazole,     2-(3′,5′-di-tert-amyl-2′-hydroxyphenyl)benzotriazole,     2-(3′,5′-bis(α,α-dimethylbenzyl)-2′-hydroxyphenyl)benzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-(2-octyloxycarbonylethyl)phenyl)-5-chlorobenzotriazole,     2-(3′-tert-butyl-5′-[2-(2-ethylhexyloxy)carbonylethyl]-2′-hydroxyphenyl)-5-chlorobenzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-(2-methoxycarbonylethyl)phenyl)-5-chlorobenzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-(2-methoxycarbonylethyl)phenyl)benzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-(2-octyloxycarbonylethyl)phenyl)benzotriazole,     2-(3′-tert-butyl-5′-[2-(2-ethylhexyloxy)carbonylethyl]-2′-hydroxyphenyl)benzotriazole,     2-(3′-dodecyl-2′-hydroxy-5′-methylphenyl)benzotriazole,     2-(3′-tert-butyl-2′-hydroxy-5′-(2-isooctyloxycarbonylethyl)phenylbenzotriazole,     2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazole-2-ylphenol];     the transesterification product of     2-[3′-tert-butyl-5′-(2-methoxycarbonylethyl)-2′-hydroxyphenyl]-2H-benzotriazole     with polyethylene glycol 300;     where R=3′-tert-butyl-4′-hydroxy-5′-2H-benzotriazol-2-ylphenyl,     2-[2′-hydroxy-3′-(α,α-dimethylbenzyl)-5′-(1,1,3,3-tetramethylbutyl)phenyl]benzotriazole;     2-[2′-hydroxy-3′-(1,1,3,3-tetramethylbutyl)-5′-(α,α-dimethylbenzyl)phenyl]benzxotriazole -   2.2. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy,     4-octyloxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy,     4,2′,4′-trihydroxy and 2′-hydroxy-4,4′-dimethoxy derivatives. -   2.3. Esters of substituted and unsubstituted benzoic acids, for     example 4-tert-butylphenyl salicylate, phenyl salicylate,     octylphenyl salicylate, dibenzoyl resorcinol,     bis(4-tert-butylbenzoyl)resorcinol, benzoyl resorcinol,     2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate,     hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl     3,5-di-tert-butyl-4-hydroxybenzoate,     2-methyl-4,6-di-tert-butylphenyl     3,5-di-tert-butyl-4-hydroxybenzoate. -   2.4. Acrylates, for example ethyl α-cyano-β,β-diphenylacrylate,     isooctyl α-cyano-β,β-diphenylacrylate, methyl     α-carbomethoxycinnamate, methyl α-cyano-β-methyl-p-methoxycinnamate,     butyl α-cyano-β-methyl-p-methoxycinnamate, methyl     α-carbomethoxy-p-methoxycinnamate and     N-(β-carbomethoxy-β-cyanovinyl)-2-methylindoline. -   2.5. Nickel compounds, for example nickel complexes of     2,2′-thiobis[4-(1,1,3,3-tetramethylbutyl)phenol], such as the 1:1 or     1:2 complex, with or without additional ligands such as     n-butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickel     dibutyldithiocarbamate, nickel salts of the monoalkyl esters, e.g.     the methyl or ethyl ester, of     4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid, nickel complexes     of ketoximes, e.g. of 2-hydroxy-4-methylphenylundecylketoxime,     nickel complexes of 1-phenyl-4-lauroyl-5-hydroxypyrazole, with or     without additional ligands. -   2.6. Sterically hindered amines, for example     bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,     bis(2,2,6,6-tetramethyl-4-piperidyl)succinate,     bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,     bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate,     bis(1,2,2,6,6-pentamethyl-4-piperidyl)     n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonate, the condensate of     1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and     succinic acid, linear or cyclic condensates of     N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and     4-tert-octylamino-2,6-di-chloro-1,3,5-triazine,     tris(2,2,6,6-tetramethyl-4-piperidyl)nitrilotriacetate,     tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate,     1,1′-(1,2-ethanediyl)-bis(3,3,5,5-tetramethylpiperazinone),     4-benzoyl-2,2,6,6-tetramethylpiperidine,     4-stearyloxy-2,2,6,6-tetramethylpiperidine,     bis(1,2,2,6,6-pentamethylpiperidyl)-2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)malonate,     3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione,     bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate,     bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)succinate, linear or     cyclic condensates of     N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and     4-morpholino-2,6-dichloro-1,3,5-triazine, the condensate of     2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazine     and 1,2-bis(3-aminopropylamino)ethane, the condensate of     2-chloro-4,6-di-(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazine     and 1,2-bis(3-aminopropylamino)ethane,     8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione,     3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione,     3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione,     a mixture of 4-hexadecyloxy- and     4-stearyloxy-2,2,6,6-tetramethylpiperidine, a condensate of     N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and     4-cyclohexylamino-2,6-dichloro-1,3,5-triazine, a condensate of     1,2-bis(3-aminopropylamino)ethane and 2,4,6-trichloro-1,3,5-triazine     as well as 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No.     [136504-96-6]); a condensate of 1,6-hexanediamine and     2,4,6-trichloro-1,3,5-triazine as well as N,N-dibutylamine and     4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No.     [192268-64-7]);     N-(2,2,6,6-tetramethyl-4-piperidyl)-n-dodecylsuccinimide,     N-(1,2,2,6,6-pentamethyl-4-piperidyl)-n-dodecylsuccinimide,     2-undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4,5]decane,     a reaction product of     7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa-3,8-deaza-4-oxospiro-[4,5]-decane     and epichlorohydrin,     1,1-bis(1,2,2,6,6-pentamethyl-4-peperidyloxycarbonyl)-2-(4-methoxyphenyl)ethene,     N,N′-bis-formyl-N,N′-bis(2,2,6,6-tetramethyl-4-peperidyl)hexamethylenediamine,     a diester of 4-methoxymethylenemalonic acid with     1,2,2,6,6-pentamethyl-4-hydroxypiperidine,     poly[methylpropyl-3-oxy-4-(2,2,6,6-tetramethyl-4-piperidyl)]siloxane,     a reaction product of maleic acid anhydride-α-olefin copolymer with     2,2,6,6-tetramethyl-4-aminopiperidine or     1,2,2,6,6-pentamethyl-4-aminopiperidine. -   2.7. Oxamides, for example 4,4′-dioctyloxyoxanilide,     2,2′-diethoxyoxanilide, 2,2′-dioctyloxy-5,5′-di-tert-butoxanilide,     2,2′-didodecyloxy-5,5′-di-tert-butoxanilide,     2-ethoxy-2′-ethyloxanilide, N,N′-bis(3-dimethylaminopropyl)oxamide,     2-ethoxy-5-tert-butyl-2′-ethoxanilide and its mixture with     2-ethoxy-2′-ethyl-5,4′-di-tert-butoxanilide, mixtures of o- and     p-methoxy-disubstituted oxanilides and mixtures of o- and     p-ethoxy-disubstituted oxanilides. -   2.8. 2-(2-Hydroxyphenyl)-1,3,5-triazines, for example     2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine,     2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2,4-bis(2-hydroxy-4-propylo     xyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine,     2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4-methylphenyl)-1,3,5-triazine,     2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2-(2-hydroxy-4-tridecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2-[2-hydroxy-4-(2-hydroxy-3-butyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine,     2-[2-hydroxy-4-(2-hydroxy-3-octyloxypropyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine,     2-[4-(dodecyloxy/tridecyloxy-2-hydroxypropoxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2-[2-hydroxy-4-(2-hydroxy-3-dodecyloxypropoxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,     2-(2-hydroxy-4-hexyloxy)phenyl-4,6-diphenyl-1,3,5-triazine,     2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine,     2,4,6-tris[2-hydroxy-4-(3-butoxy-2-hydroxypropoxy)phenyl]-1,3,5-triazine,     2-(2-hydroxyphenyl)-4-(4-methoxyphenyl)-6-phenyl-1,3,5-triazine,     2-{2-hydroxy-4-[3-(2-ethylhexyl-1-oxy)-2-hydroxypropyloxy]phenyl}-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine. -   3. Metal deactivators, for example N,N′-diphenyloxamide,     N-salicylal-N′-salicyloyl hydrazine, N,N′-bis(salicyloyl)hydrazine,     N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine,     3-salicyloylamino-1,2,4-triazole, bis(benzylidene)oxalyl     dihydrazide, oxanilide, isophthaloyl dihydrazide, sebacoyl     bisphenylhydrazide, N,N′-diacetyladipoyl dihydrazide,     N,N′-bis(salicyloyl)oxalyl dihydrazide,     N,N′-bis(salicyloyl)thiopropionyl dihydrazide. -   4. Phosphites and phosphonites, for example triphenyl phosphite,     diphenylalkyl phosphites, phenyldialkyl phosphites,     tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl     phosphite, distearylpentaerythritol diphosphite,     tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol     diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol     diphosphite, bis(2,4-di-cumylphenyl)pentaerythritol diphosphite,     bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,     diisodecyloxypentaerythritol diphosphite,     bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite,     bis(2,4,6-tris(tert-butylphenyl)pentaerythritol diphosphite,     tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)     4,4′-biphenylene diphosphonite,     6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin,     bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite,     bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite,     6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin,     2,2′,2″-nitrilo-[triethyltris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite],     2-ethylhexyl(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite,     5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane. -   5. Hydroxylamines, for example N,N-dibenzylhydroxylamine,     N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine,     N,N-dilaurylhydroxylamine, N,N-ditetradecylhydroxylamine,     N,N-dihexadecylhydroxylamine, N,N-dioctadecylhydroxylamine,     N-hexadecyl-N-octadecylhydroxylamine,     N-heptadecyl-N-octadecylhydroxylamine, N,N-dialkylhydroxylamine     derived from hydrogenated tallow amine. -   6. Nitrones, for example N-benzyl-alpha-phenylnitrone,     N-ethyl-alpha-methylnitrone, N-octyl-alpha-heptylnitrone,     N-lauryl-alpha-undecylnitrone, N-tetradecyl-alpha-tridecylnitrone,     N-hexadecyl-alpha-pentadecylnitrone,     N-octadecyl-alpha-heptadecylnitrone,     N-hexadecyl-alpha-heptadecylnitrone,     N-ocatadecyl-alpha-pentadecylnitrone,     N-heptadecyl-alpha-hepta-decylnitrone,     N-octadecyl-alpha-hexadecylnitrone, nitrone derived from     N,N-dialkylhydroxylamine derived from hydrogenated tallow amine. -   7. Thiosynergists, for example dilauryl thiodipropionate or     distearyl thiodipropionate. -   8. Peroxide scavengers, for example esters of β-thiodipropionic     acid, for example the lauryl, stearyl, myristyl or tridecyl esters,     mercaptobenzimidazole or the zinc salt of 2-mercaptobenzimidazole,     zinc dibutyldithiocarbamate, dioctadecyl disulfide, pentaerythritol     tetrakis(β-dodecylmercapto)propionate. -   9. Polyamide stabilisers, for example copper salts in combination     with iodides and/or phosphorus compounds and salts of divalent     manganese. -   10. Basic co-stabilisers, for example melamine,     polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea     derivatives, hydrazine derivatives, amines, polyamides,     polyurethanes, alkali metal salts and alkaline earth metal salts of     higher fatty acids, for example calcium stearate, zinc stearate,     magnesium behenate, magnesium stearate, sodium ricinoleate and     potassium palmitate, antimony pyrocatecholate or zinc     pyrocatecholate. -   11. Nucleating agents, for example inorganic substances, such as     talcum, metal oxides, such as titanium dioxide or magnesium oxide,     phosphates, carbonates or sulfates of, preferably, alkaline earth     metals; organic compounds, such as mono- or polycarboxylic acids and     the salts thereof, e.g. 4-tert-butylbenzoic acid, adipic acid,     diphenylacetic acid, sodium succinate or sodium benzoate; polymeric     compounds, such as ionic copolymers (ionomers). Especially preferred     are 1,3:2,4-bis(3′,4′-dimethylbenzylidene)sorbitol,     1,3:2,4-di(paramethyldibenzylidene)sorbitol, and     1,3:2,4-di(benzylidene)sorbitol. -   12. Fillers and reinforcing agents, for example calcium carbonate,     silicates, glass fibres, glass bulbs, asbestos, talc, kaolin, mica,     barium sulfate, metal oxides and hydroxides, carbon black, graphite,     wood flour and flours or fibers of other natural products, synthetic     fibers. -   13. Other additives, for example plasticisers, lubricants,     emulsifiers, pigments, rheology additives, catalysts, flow-control     agents, optical brighteners, flameproofing agents, antistatic agents     and blowing agents. -   14. Benzofuranones and indolinones, for example those disclosed in     U.S. Pat. No. 4,325,863; U.S. Pat. No. 4,338,244; U.S. Pat. No.     5,175,312; U.S. Pat. No. 5,216,052; U.S. Pat. No. 5,252,643;     DE-A-4316611; DE-A-4316622; DE-A-4316876; EP-A-0589839 or     EP-A-0591102 or     3-[4-(2-acetoxyethoxy)phenyl]-5,7-di-tert-butylbenzofuran-2-one,     5,7-di-tert-butyl-3-[4-(2-stearoyloxyethoxy)phenyl]-benzofuran-2-one,     3,3′-bis[5,7-di-tert-butyl-3-(4-[2-hydroxyethoxy]phenyl)benzofuran-2-one],     5,7-di-tert-butyl-3-(4-ethoxyphenyl)benzofuran-2-one,     3-(4-acetoxy-3,5-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one,     3-(3,5-dimethyl-4-pivaloyloxyphenyl)-5,7-di-tert-butylbenzofuran-2-one,     3-(3,4-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one,     3-(2,3-dimethylphenyl)-5,7-di-tert-burylbenzofuran-2-one.

The costabilizers are added, for example, in concentrations of 0.01 to 10%, relative to the total weight of the synthetic polymer to be stabilized.

Preferred further additives are phenolic antioxidants, light-stabilizers and/or processing stabilizers. Preferred further additives for the stabilization of polyurethanes are phenolic antioxidants and/or amino antioxidants of the secondary amine type (aminic antioxidants, item 1.19) and/or phosphites or phosphonites (item 4).

Of special interest is a stabilizer mixture comprising Irganox 1135 [RTM, see footnote d) at the end of Table 2], Irganox 5057 [RTM, see footnote c) at the end of Table 2] and a compound of the formula I wherein R₁ and R₂ are hydrogen, R₄ and R₄ are tert-octyl and R₅ is methyl [compound (102), see footnote f) at the end of Table 2]. Preferably the ratio by weight of Irganox 1135:Irganox 5057: compound (102) is for example 100:1:0.01 to 1:1:10. A mixture of 10:3:1 will be commercially available as Irgastab PUR 67 [RTM, Ciba Specialty Chemicals Inc.].

Also of interest is a stabilizer mixture comprising Irganox 1135 [RTM, see footnote d) at the end of Table 2], Irgafos 68 [RTM, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite] and a compound of the formula I wherein R₁ and R₂ are hydrogen, R₄ and R₄ are tert-octyl and R₅ is methyl [compound (102), see footnote f) at the end of Table 2]. The ratio by weight of Irganox 1135:Irgafos 68: compound (102) is for example 100:1:0.01 to 1:1:10. A stabilizer mixture of 7:1:1 will be commercially available as Irgastab PUR 68 [RTM, Ciba Specialty Chemicals Inc.]

The fillers and reinforcing agents (item 12 in the list), for example talc, calcium carbonate, mica or kaolin, are added to the polyolefins in concentrations, for example, of from 0.01 to 40%, based on the overall weight of the polyolefins to be stabilized.

The fillers and reinforcing agents (item 12 in the list), for example metal hydroxides, especially aluminium hydroxide or magnesium hydroxide, are added to the polyolefins in concentrations, for example, of from 0.01 to 60%, based on the overall weight of the polyolefins to be stabilized.

Carbon black as filler is added to the polyolefins in concentrations, judiciously, of from 0.01 to 5%, based on the overall weight of the polyolefins to be stabilized.

Glass fibers as reinforcing agents are added to the polyolefins in concentrations, judiciously, of from 0.01 to 20%, based on the overall weight of the polyolefins to be stabilized.

Further preferred compositions comprise in addition to components (a) and (b) further additives as well, especially alkaline earth metal salts of higher fatty acids, for example calcium stearate.

As a conventional stabilizer combination for processing synthetic polymers, for example polyolefins, to form corresponding mouldings, the combination of a phenolic antioxidant with a secondary antioxidant based on an organic phosphite or phosphonite is recommended. Depending on the particular substrate and process, however, many polyolefin processors are forced to operate processes in the high-temperature region above about 280° C. By virtue of the incorporation of the compounds of the formula I, which is specially suitable for high-temperature applications, in particular in the temperature range above 300° C., industrial materials and mouldings, based for instance on high-density polyethylene, for example pipes and their technical variants (fittings), can be produced at a greater rate and with fewer rejects. Another advantage of the compounds of the formula I is that it can be employed in very small amounts. This leads to a reduction in the overall concentration of antioxidant relative to conventional stabilizer mixtures. Thus the use of a low concentration of the compounds of the formula I allows a reduction in the overall concentration of stabilizer by about a third in polyolefins, for example, which simultaneously represent an economic advantage.

Incorporation of the compounds of the formula I and, if desired, further additives into the synthetic polymers is carried out by known methods, for example before or during moulding or else by applying the dissolved or dispersed compounds to the synthetic polymer, if appropriate with subsequent slow evaporation of the solvent. The compounds of the formula I can also be added to the synthetic polymers to be stabilized in the form of a masterbatch containing them, for example, in a concentration of 2.5 to 25% by weight.

The compounds of the formula I can also be added before or during polymerisation or before crosslinking.

The compounds of the formula I, with or without further additives, can be incorporated in pure form or encapsulated in waxes, oils or polymers into the synthetic polymer that is to be stabilized.

The compounds of the formula I, with or without further additives, can also be sprayed onto the synthetic polymer that is to be stabilized. It is able to dilute other additives (for example the conventional additives indicated above) or their melts so that they too can be sprayed together with these additives onto the polymer that is to be stabilized. Addition by spraying on during the deactivation of the polymerization catalysts is particularly advantageous, it being possible to carry out spraying using, for example, the steam used for deactivation.

In the case of spherically polymerized polyolefins it may, for example, be advantageous to apply the compounds of the formula I, with or without other additives, by spraying.

The materials stabilized in this way can be employed in a wide variety of forms, for example as foams, films, fibres, tapes, moulding compositions, as profiles or as binders for coating materials, especially powder coatings, adhesives or putties.

The polyolefins stabilized in this way can likewise be employed in a wide variety of forms, especially as thick-layer polyolefin mouldings which are in long-term contact with extractive media, such as, for example, pipes for liquids or gases, films, fibres, geomembranes, tapes, profiles or tanks.

The preferred thick-layer polyolefin mouldings have a layer thickness of from 1 to 50 mm, in particular from 1 to 30 mm, for example from 2 to 10 mm.

As already mentioned, thermoplastic polymers are protected with particular advantage. Attention should be drawn above all in this context to the outstanding activity of the compounds of the formula I as in-process stabilizer (heat stabilizer). For this purpose the compounds of the formula I are advantageously added to the synthetic polymer prior to or during its processing. However, other polymers too (for example elastomers) or lubricants or hydraulic fluids can be stabilized against degradation, for example light-induced or thermooxidative degradation. Elastomers can be taken from the above listing of possible synthetic polymers.

The lubricants and hydraulic fluids in question are based, for example, on mineral oils or synthetic oils or on mixtures thereof. The lubricants are familiar to the skilled person in the art and are described in the relevant technical literature, for example in Dieter Klamann, “Schmierstoffe und verwandte Produkte” (Verlag Chemie, Weinheim, 1982), in Schewe-Kobek, “Das Schmiermittel-Taschenbuch” (Dr. Alfred Hüthig-Verlag, Heidelberg, 1974) and in “Ullmanns Enzyklopādie der technischen Chemie”, Vol.13, pages 85-94 (Verlag Chemie, Weinheim, 1977).

The present invention also relates to a process for stabilizing a synthetic polymer against oxidative, thermal or light-induced degradation, which comprises incorporating therein or applying thereto at least a compound of the formula I.

A preferred embodiment of the present invention is therefore the use of the compounds of the formula I as stabilizers, especially in-process stabilizer (thermal stabilizer), for synthetic polymers, especially thermoplastic polymers, against oxidative, thermal or light-induced degradation.

The examples which follow illustrate the invention in more detail. Parts and percentages are by weight.

EXAMPLE 1 Preparation of Polyether/Polyurethane Soft Foams as well as the Stabilization Thereof

2 g (0.025%, based on the polyol) of a stabilizer according to Table 1 is dissolved in 8 kg of a polyether polyol, Lupranol 2045 (RTM) (trifunctional polyether polyol having primary hydroxyl groups; hydroxyl number 35 mg KOH/g, water content less than 0.1%, acid number less than 0.1 mg KOH/g) which contains 6 g of Irganox 5057 (RTM) [see footnote c) at the end of Table 2] and 4 g of Irganox 1135 (RTM) [see footnote d) at the end of Table 2]. 520 g of a solution consisting of 120 g Tecostab (RTM) (polysilicone supplied by Goldschmidt, Germany], and 6.4 g diazabicyclooctane (amine catalyst) are added and the reaction mixture is stirred vigorously for 60 seconds at 100 rpm. 14.4 g of tin octoate and 120 g (1.5%, based on the polyol) of diphenyl isodecyl phosphite (DPDP) is then added and the reaction mixture is again stirred vigorously for 60 seconds at 100 rpm. With vigorous stirring, 5.11 kg of an isocyanate [Lupranat T80 (RTM), supplied by BASF; toluylene-2,4- and toluylene-2,6-diisocyanate mixture] are then added immediately and the mixture is poured into a lined mould and the exothermic temperature is measured during foaming to a foam block. The foam blocks are cooled and stored at room temperature for 24 hours. The next day the foams are cut. The color of the foam blocks is determined visually. The whiter the foam the better is the foam stabilized. It has to be noted that this effect is only visible on large foaming scale (for example 1 m³ foam. The observation of this effect is difficult on a lab scale. The results are summarized in Table 1.

TABLE 1 Color of the foam Example Stabilizer Visual observation 1a a) — slightly yellow 1b a) 0.025% Compound (101) e) yellow/pink 1c b) 0.025% Compound (102) f) white See explanations of footnotes at the end of Table 2.

EXAMPLE 2 Preparation of ABS (Acrylonitrile-Butadiene-Styrene) as well as the Stabilization Thereof

833 g of Acrylonitrile-butadiene-styrene graft polymer [Baymod 60A (RTM), Bayer Corp.], 1667 g of styrene-acrylonitrile copolymer [Lustran 32 (RTM), Bayer Corp.], 26.25 g of N,N′-ethylenedi(stearamide), 1.496 g of Irganox 1076 [(RTM), n-octadecyl 3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, 0.057% based on polymer], 2.993 g of Irgafos 168 [(RTM), tris-(2,4-di-tert-butylphenyl) phosphite, 0.113% based on polymer] and 0.788 g of a stabilizer according to Table 2 (0.030% based on polymer) were mixed together on a tumbling barrel mixer during 15 hours. The resulting dry-blend was then compounded on twin-screw-extruder (Berstorff 46D, at 220° C., 110 rpm and 12 kg/h) and, after drying for 3 h at 80° C., injection molded on an Engel HL65 Injection Molder at 240° C. (cycle time: 35.8 s; injection speed: 25 mm/s; mold temperature: 60° C.) to give natural ABS plaques of the dimension 67×64×2 mm.

The initial color of these ABS plaques was measured, then the plaques were exposed to accelerated weathering in a Weather-O-Meter ATLAS Ci 65 for 1000 hours under the following conditions: Irradiation 0.35 W/m² at 340 nm; Borosilicate inner and outer filter; Black Panel Temperature: 63° C.; no dark phase; 60% relative humidity and dry cycle (no rain). The yellowness index (YI) is determined according to DIN 6167. Low YI values denote little discoloration, high YI values high discoloration of the samples. The less discoloration, the more effective the stabilizer. The results are summarized in Table 2.

TABLE 2 Example Stabilizer Yellowness index 2a a) — >100 2b a) 0.030% compound (101) e) 50.6 2c b) 0.030% compound (102) f) 49.6 A difference of 1 unit in the yellowness index (YI) is considered by persons skilled in the art as clearly relevant. a) Comparison examples. b) Example according to the invention. c) Irganox 5057 (RTM) (Ciba Specialty Chemicals) is a secondary  amine antioxidant and is a technical mixture, obtained by  reaction of diphenylamine with diisobutylene, comprising a′) 3% of diphenylamine; b′) 14% of 4-tert-butyldiphenylamine; c′) 30% of compounds of the group i) 4-tert-octyldiphenylamine, ii) 4,4′-di-tert-butyldiphenylamine, iii) 2,4,4′-tris-tert-butyldiphenylamine; d′) 29% of the compounds of the group i) 4-tert-butyl-4′-tert-octyldiphenylamine, ii) o,o′-, m,m′- or p,p′-di-tert-octyldiphenylamine, iii) 2,4-di-tert-butyl-4′-tert-octyldiphenylamine; e′) 24% of the compounds of the group i) 4,4′-di-tert-octyldiphenylamine and ii) 2,4-di-tert-octyl-4′-tert-butyldiphenylamine. d) Irganox 1135 (RTM) (Ciba Specialty Chemicals) is a phenolic  antioxidant of the formula AO-1. (AO-1)

e) Compound (101) is a mixture of about 85 parts by weight of the  compound of the formula Va and about 15 parts by weight of  the compound of the formula Vb. (Va)

(Vb)

f) Compound (102) according to the instant invention is a compound  of the formula I′. (I′) 

1. A composition comprising a) a synthetic polymer subject to oxidative, thermal or light-induced degradation; and b) at least a compound of the formula I

wherein R₁ and R₂ are each independently of one another hydrogen or C₁-C₈alkyl, R₃ and R₄ are each tert-octyl, and R₅ is C₁-C₇alkyl.
 2. A composition according to claim 1, wherein R₁ and R₂ are each independently of one another hydrogen or C₁-C₄alkyl, and R₅ is C₁-C₄alkyl.
 3. A composition according to claim 1, R₁ and R₂ are hydrogen, R₃ and R₄ are tert-octyl, and R₅ is methyl.
 4. A composition according to claim 1, comprising as component (a) a thermoplastic polymer.
 5. A composition according to claim 1, comprising as component (a) a polyolefin, polyether polyol or polyurethane.
 6. A composition according to claim 1, wherein component (b) is present in an amount of 0.0005 to 10% based on the weight of component (a).
 7. A composition according to claim 1, comprising components (a) and (b) and further additives.
 8. A composition according to claim 7, where the further additives are phenolic antioxidants, light-stabilizers or processing stabilizers.
 9. A process for stabilizing a synthetic polymer against oxidative, thermal or light-induced degradation, which comprises incorporating therein or applying thereto at least a compound of the formula I according to claim
 1. 